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think you need to flocculate with bentonite or Epsom salts Addition of 2% bent.  and add a little Mg Sulphate up to 2% in solution to the glaze Bentonite better added and encorporated with dry glaze ingredients prior to adding to liquid.

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Bentonite will help with hard-panning.  Dissolve it in some hot water before adding it to the already mixed glaze.  Dissolve epsom salts in hot water until the salts stop dissolving; then add a teaspoon or so to the glaze until it stops hard-panning. 

 

You can add gum Arabic or glycerin to make the glaze brushable. 

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To keep a glaze in suspension:

Add 2% bentonite and 0.5% Epsom Salts. The bentonite needs to be added during the weighing process and dry mixed well or it will clump. The Epsom Salts should be dissolved in water and added to the wet mix after sieving. There will be a noticeable thickening of the glaze upon adding it, and additional water may need to be added.

 

To make a glaze brushable:

Make gum solution by adding 2 tablespoons CMC gum and 1/8 teaspoon copper carbonate (preservative) to a gallon of warm water. Let it sit overnight, then blend till smooth. Substitute 1/3 of the water in the glaze with gum solution.

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To keep a glaze in suspension:

Add 2% bentonite and 0.5% Epsom Salts. The bentonite needs to be added during the weighing process and dry mixed well or it will clump. The Epsom Salts should be dissolved in water and added to the wet mix after sieving. There will be a noticeable thickening of the glaze upon adding it, and additional water may need to be added.

 

To make a glaze brushable:

Make gum solution by adding 2 tablespoons CMC gum and 1/8 teaspoon copper carbonate (preservative) to a gallon of warm water. Let it sit overnight, then blend till smooth. Substitute 1/3 of the water in the glaze with gum solution.

 

Hi Neil

 

Copper carbonate as a preservative?    16 years in ceramics and that's new to me....how wonderful!....never used it for that.

 

Also, know that 1/8 tsp of copper carb is very little but it would add, or vary existing colour in 1 gallon mix?     

 

Intriguing answers, details please?

 

 

ta,

Irene

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To keep a glaze in suspension:

Add 2% bentonite and 0.5% Epsom Salts. The bentonite needs to be added during the weighing process and dry mixed well or it will clump. The Epsom Salts should be dissolved in water and added to the wet mix after sieving. There will be a noticeable thickening of the glaze upon adding it, and additional water may need to be added.

 

To make a glaze brushable:

Make gum solution by adding 2 tablespoons CMC gum and 1/8 teaspoon copper carbonate (preservative) to a gallon of warm water. Let it sit overnight, then blend till smooth. Substitute 1/3 of the water in the glaze with gum solution.

 

Hi Neil

 

Copper carbonate as a preservative?    16 years in ceramics and that's new to me....how wonderful!....never used it for that.

 

Also, know that 1/8 tsp of copper carb is very little but it would add, or vary existing colour in 1 gallon mix?     

 

Intriguing answers, details please?

 

 

ta,

Irene

 

 

CMC Gum will get eaten up by bacteria if you don't use a preservative, and the brushability will decline. Copper is a great preservative- it's why treated lumber is green. The small amount used in the gum solution will not color the glaze.

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I am extremely familiar with this recipe. It doesn't need any bentonite. The EPK content is enough to keep it suspended, if you use vinegar or Epsom salt soloution to flocculate, as Neil described. After that, it works a treat.

Diesel Clay, when you are using this glaze without Bentonite it doesn't hardpan?

If it does how does one know not to add Bentonite and only Mg Sulphate?

 

Neil, thanks I have used CMC to make majolica onglaze colurs more "painterly" but never used it in a glaze so will try this when brushing on glazes in future.

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Babs, it hard pans without the bentonite if you don't stir it up at least once a month. It will also hard pan with the bentonite if you don't stir it up once a month. Adding the bentonite alone doesn't stop the hard panning.

 

When you add bentonite to a glaze that has lots of frit in it that has lots of (relatively) small and uniform particle sizes for example, you're introducing something that has some large and medium sized particles to the mix. These more varied particle sizes slow all the small frit particles down when they're trying to sink straight to the bottom of the bucket to make that charming cement-like layer we all know and hate. When you add a few spoons of a saturated Epsom salt soloution to a glaze bucket, it changes the polarity of the water so that this particle-floating effect is even more pronounced, and lasts a bit longer. It will also stop your pot from absorbing The water out of your glaze as rapidly, so that it has a chance to smooth out on the pot, minimizing drip marks. The down side of this is that it takes longer for the glaze to dry. It's kind of like adding an extender to house paint.

 

You typically only add bentonite to a glaze recipe that has less than 5% clay of some kind, or any gerstley borate, which while in the bucket acts like clay for the purposes of keeping the particles suspended in water. Clays usually already have the variety of particle sizes, because they're not milled within an inch of their lives for uniformity like frit is. If there's 10% clay of any kind in a glaze already, you just have to add the Epsom salt (or vinegar, which does the same thing).

 

Edit: if you add too much bentonite to a glaze, it can gel in the bucket, which will make you think you've got more glaze on the pot than you do, and then you wonder why it went all weird and streaky like that.

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Thanks Deisel Clay. I appreciate the explanation. I'll look out for the things you have described. Interesting that the Epsom salts slow the drying process Ie take up of water does this in fact change the layering of glaze on the pot like thin it?

Has SPring come to your part of Canada yet?

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Having a flocculated glaze (with the Epsom salt, et al) is supposed to make it so that the layer of glaze is uniform, no matter the porosity of your bisque, or how long you dip for. It can be handy if you have a clay body that has lots of organic matter, like carbon or sulphur, that you want to burn off with a higher bisque temperature so that your glaze pinholes less.

(I just spent the afternoon on digitalfire!)

 

And it was about 27 degrees C (!!!) here last week, but it's dropped down to a more seasonable 4 with drizzle this evening. How's your neck of the woods looking?

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Pleasant 24ish C that is with a nor'easterly so a warm wind here.

Just damaged my left knee in sheep yard so  a bit disgruntled. Don't take your eye off the animals in yards is my tip of the day.These pregnant mummas are about 1/12 times my body weight and my dog was just a little pushy.

Thanks for all the info on the effects of flocculants.

Id my knee doesn't start playing the game I may be researching lots...

Feeling for you Mark, must be suffering.

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  • 3 months later...

the title of this thread is cornstarch and just in case anyone new is reading this old discussion, cornstarch is not a glaze ingredient.  AT ALL!  so far, nobody has addressed the original question.  no, do not add it to your glaze.

 

some potters use dry cornstarch dusted over a clay slab so it can be impressed with a material that might stick to the clay without the layer of cornstarch separating the two.  something like a glass or metal shape to give depth or texture to the slab.

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I use cornstarch on the bisque molds I have made to use as supports for my silkscreened pieces. It seems to help with the lift off and doesn't make the silkscreen image smear.

 

I also dip my jewelry cutters in it to get cleaner edges out of the clay shape so there's less clean up.

 

I've never used it in the studio with a liquid glaze to thicken it but HAVE used it in the kitchen to thicken gravy.

 

T

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Was one of my "turned on" days, kids used to hate them, preferred when I was in my dream state :D But you were right, we hadn't stated  that corn starch could not be used..anyone tried it? CMC burnes out, Glycerine burns out..whyat's so special that corn starch would be so bad?  Flaky when dries out? Rats eat it off your pots?

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Was one of my "turned on" days, kids used to hate them, preferred when I was in my dream state :D But you were right, we hadn't stated  that corn starch could not be used..anyone tried it? CMC burnes out, Glycerine burns out..whyat's so special that corn starch would be so bad?  Flaky when dries out? Rats eat it off your pots?

 

I ended up trying it.... So this is what went down, It lacked any kind of binding at all, I mean it felt like it made it even more flakier. It ended up cracking apart and falling off in chunks that would instantly turn into powder when they hit the table. Also applying it was a nightmare, instant dry out when applied to the pot. I felt bad for wasting the tin oxide in the test :/

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I have found that often just getting the right chemicals is really the best approach when it come to these substitution ideas.

The up side is you learn more about the chemicals-the down side is it does not work and you have lost the materials and the time.

This reminds me I need to fill my 3 powder bears with cornstach

 

PS I used to use talc for the dry suit seals but cornstarch is more friendly.

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